core prac 2 Flashcards
state the dv for this paractical , describe how this was established/measured
the volume of fruit juice needed to decolourise 1 cm^3 DCPIP
measured by titrating the juice into a test tube containing dcpip until the dcpip turns colourless and seeing how much less juice is left in the syringe
state cvs for this practical, describe how these were established/measured
-concentration of DCPIP
measured using a syringe
-age of fruit
longer storage results in the breakdown of vit c
-storage temp
all stored in a fridge at 8 degrees c as lower temps preserve vit c for longer
explain how to establish vitamin c content
-work out the mean results from standard sample sets of known concentrations of vitamin c
-plot these on a graph of vitamin c content (mg cm^-3) against volume to decolourise DCPIP (cm^3)
-draw a calibration curve of all the points plotted
-take the result for the volume to decolourise DCPIP from each fruit and draw a horizontal line from there until it meets the calibration curve then draw a vertical line from that point, where this like intercepts the x-axis is the vitamin c content for that fruit
devise an investigation to look at the effect of vit c content of carrots
-boil carrots with lid on to ensure no water evaporates
-take samples to test for vitamin c content from the carrot water multiple times throughout the experiment and titrate these into test tubes containing 1cm^3 of 1% DCPIP until it decolourises
-when the volume of carrot water required to decolourise DCPIP stops decreasing the carrot water used contains the same amount of vitamin c that the carrots would have
-use a calibration curve of known bit c contents to see the bit c content of the carrots
state the iv for this practical & how its established/measured
type of citrus fruit
what is the method for the titration in this practical
1.Pipette 1cm3 of 1% blue DCPIP into a test tube.
2. Use an accurate pipette to add 1 drop of the first fruit juice to the same test tube and then shake the mixture 3 times.
3. Continue to add drops and shake the contents of the test tube until the blue colour of the DCPIP disappears. Note down the volume of fruit juice that was used up.
4. Collect data for the other fruit juices available. Repeats can be carried out to calculate mean results.
what is the method for this practical
Using a syringe, measure set volume of DCPIP into a test tube
Using a syringe, titrate juice into DCPIP until the DCPIP decolorises
Record the volume of juice added in cm3
Repeat steps 1-3 two more times to calculate the mean volume of juice needed
Use a calibration curve* to calculate the vitamin C content
